1. Field of the Invention
The present invention relates to radiation detector crystals for detecting, among other things, X-ray and gamma-ray radiation and to a method of forming said crystals.
2. Description of Related Art
It is known in the art that doped Indium-Phosphide (InP) crystals, made from elements in columns III and V of the periodic table of the elements, can be used to form high speed Integrated Circuits (ICs), lightwave communication devices, such as semiconductor lasers useful for fiber optic communications, and the like. See, e.g., K. M. Yu and M. C. Ridgway, Appl. Phys. Lett 37, pp. 52-54 (1998); K. M. Yu and M. C. Ridgway, Nucl. Instrum. Methods B 168, pp. 65-71 (2000); “Ruthenium: A New Thermally Stable Compensator in InP”, Int. Conf. On InP and Related Material, pp. 11-15, May 1998, Tsukuba, Japan; “Ruthenium Doped High-Power 1.48 μm SIPBH Laser”, Int. Conf. On InP and Related Material, pp. 16-20, May 1999, Davos, Switzerland; “Ruthenium—a superior compensator of InP”, A. Dadgar et al., Applied Physics Letters 28, December 1998; “Growth of Ru doped semi-insulating InP by low pressure metal organic chemical vapor deposition”, A. Dadgar et al., Proc. of the 9th IC-MOVPE, La Jolla, Calif. (1998); and U.S. Pat. No. 4,642,799 to Glass. However, it is also known in the art that doped InP is not best for X-ray and Gamma ray radiation detection.
In contrast, it is known in the art that doped CdxZn1-xTe, where 0≦x≦1, made from elements in columns II and VI of the periodic table of the elements, can be used to form radiation detector crystals. See, e.g., U.S. Patent Application Publication No. US 2003/0209184 to Kazandjian et al., filed Mar. 5, 2003; “Thermally Stimulated Current Measurement Of Traps In Detector-Grade CdTe”, Barnes and Zanio, IEEE Trans. Nucl. Sci. NS-23, p. 177 (1976); “PL In High-Resistivity CdTe:In”, Barnes and Zanio, J. Appl. Phys. 46, p. 3959 (1975); “Evidence of Deep Donor in CdTe”. Kuhn, Ossau, Waag, Bicknell-Tassius and Landwher, J. Crystal Growth, v. 117, p. 660 (1992); and “Chlorine-Related Photoluminescence Lines In High-Resistivity Cl-Doped CdTe”, Seto, Tanaka, Mase and Kawashima, J. Crystal Growth, v. 117, p. 271 (1992).
Because (1) InP and (2) CdxZn1-xTe, where 0≦x≦1, are formed from different elements from the periodic table of the elements, it is believed by the present inventors, that those skilled in the art would not consider using doping techniques applicable to InP, used to form high speed ICs and lightwave communication devices, for doping CdxZn1-xTe, where 0≦x≦1, to form radiation detector crystals for detecting high energy radiation events. Moreover, as best known by the present inventors, the literature is also silent regarding the applicability and desirability of forming CdxZn1-xTe, where 0≦x≦1, radiation detector crystals utilizing doping techniques used to make InP crystals used to form ICs and lightwave communication devices.